A look at how how winter 2021-22 is panning out vs the winter forecast

[Nick F]

A look at how and why the Netweather 2021-22 Winter Forecast is not really matching how the winter is playing out in reality.

View the full blog here

[Dorsetbred]

Great article and food for thought for many people, considering a forecast for next winter, thanks for all your hard work in preparing the articles.

 

[North-Easterly Blast]

I really think that last year's very warm September has ruined this winter from a cold perspective, as it is a well known fact of the UK's weather patterns that it is very rare to get a cold winter after a really warm September.  My view is, and looking at past records, it appears that a really warm September is more likely to be followed by milder conditions during the winter, and warm Septembers certainly do not bode well for cold patterns to develop in the following winter, and this winter the "warm September theory" has clearly struck again.

Some years ago I believe that the Met Office used SSTs in May to forecast the following May's NAO state.  I find that in some ways hard to believe that May SSTs affect the following winter's NAO; as the only reason that I can think of is that there must be a correlation between SSTs in May and similar SST anomalies occurring seven to ten months later.  That said I believe that the warm September theory is more significant, as it appears that, whilst it is not clear that there is any trend between cool or average September CETs and the following winters weather patterns, it appears that if synoptic patterns occur that result in a high September CET, they do not favour cold patterns to develop for the UK during the following winter, three to six months later.

Edited February 7, 2022 by North-Easterly Blast

[Wold Topper]

I thought the 'mild' September, mild winter 'theory' had been thoroughly debunked already? Just from what i have read, please feel free to correct my assertion,

[MP-R]

1 hour ago, Wold Topper said:

I thought the 'mild' September, mild winter 'theory' had been thoroughly debunked already? Just from what i have read, please feel free to correct my assertion,

There's an undeniable propensity for warm Septembers to be followed by a milder winter, but no causation has been proven, as otherwise that would be the case all the time, which it isn't.

[damianslaw]

I guess the key question going forward is what factors enable weak and strong PV formation.. seems this year though the signals have gone bust as they were favouring to override the PV. 

 

[North-Easterly Blast]

On 07/02/2022 at 23:17, MP-R said:

There's an undeniable propensity for warm Septembers to be followed by a milder winter, but no causation has been proven, as otherwise that would be the case all the time, which it isn't.

In recent decades at least the warm September theory of being followed by a milder winter has certainly existed and shown up.  That said it has still been shown that it is still possible to have a September CET that is around the 1991-2020 average but slightly above average and get a cold winter after it, like in 2009 and 1978.  In recent decades the warmest September CET that I can think of was 1985s 14.6 that was followed by a colder winter.  After a high September CET like last year's was, the trend is clear that they are mostly followed by a milder winter or at least a winter with little in the way of cold outbreaks in it.  Although no-one can accurately forecast the UKs weather years into the future, if I was making a forecast, I would say that it is highly unlikely that there will ever be a cold winter in any given year following a warm September in terms of overall CET.

I do not know what went wrong with past winters that have delivered next to nothing in terms of cold in the UK, but I have a pretty good idea that in 2015-16 it was ENSO Strong El Nino forcing, and in 2019-20 strong IOD forcing, and in 2021-22 and 2016-17 it was the very warm September before it.

Edited February 9, 2022 by North-Easterly Blast